In a semiconductor manufacturing process, creating a rugged polysilicon layer is a popular way to increase the utilizable surface area of electrode plates of a capacitor so as to increase the charge capacity of the capacitor. It is especially often used for manufacturing storage capacitors of a dynamic random access memory (DRAM). However, when the element arrangement in a semiconductor chip is getting denser or the size of the semiconductor chip is getting smaller as is the current trend, the utilizable surface area provided by the conventional rugged polysilicon layer (refer to the structure shown FIG. 1A) will become insufficient.